Stormy Daniels’ claim of an affair with US President Donald Trump has no credibility because she is an adult film star, and first lady Melania Trump “knows it’s not true”, Trump’s lawyer, Rudy Giuliani, has said.

Giuliani’s comments, made Wednesday at a financial conference in Tel Aviv, Israel, drew a heated response on Thursday from Daniels’s lawyer, Michael Avenatti, who called for the president to immediately fire Giuliani.

Daniels has said she had sex with Trump in 2006, just months after his wife, Melania, gave birth to their son Barron. She is fighting to invalidate a nondisclosure agreement she signed days before the 2016 election.

Trump has denied Daniels’s contention, and Giuliani said that the US$130,000 Trump paid Daniels for her silence “tells me it’s not true”.

He said that if Daniels, whose real name is Stephanie Clifford, could prove her story she would have demanded millions of dollars and called the payoff a “nuisance thing” to “get rid of it”.

“I don’t even think there is the slightest suspicion that it’s true,” Giuliani said. “Excuse me, but when you look at Stormy Daniels? I know Donald Trump, look at his three wives, beautiful women, classy women, women of great substance. Stormy Daniels?”

“I’m sorry, I don’t respect a porn star the way I respect a career woman, or a woman of substance, or a woman who has great respect for herself,” he went on.

“So, Stormy, you want to bring a case? Let me cross-examine you. Because the business you are in entitles you to no degree of giving your credibility any weight.”

He said Daniels “should be celebrated for her courage, strength and intelligence” and that he “would put her character up against Mr. Giuliani’s any day of the week”.

“His most recent comments regarding my client, who passed a lie detector test and who the American people believe, are disgusting and a disgrace,” Avenatti said.

My client @StormyDaniels should be celebrated for her courage, strength and intelligence. She is one of the most credible people I have ever met regardless of gender. Period. I would be put her character up against Mr. Giuliani’s any day of the week. #Basta

Giuliani declined to comment further on Thursday when reached by The Associated Press.

Daniels filed a lawsuit in Los Angeles on Wednesday claiming that her former lawyer, Keith Davidson, was a “puppet” for Trump and had been secretly working with Trump’s personal attorney, Michael Cohen, to get her to appear on Fox News and falsely deny the sexual tryst with Trump.